Compression check on 440 Six Pack

[KillerBee]

Planning on changing spark plugs on my 440 Six Pack and figured while they were out I would borrow a compression test kit and check the engine's compression.

I've never done a compression check and have done some reading and have some questions on the proceedure.

-First I need to get the engine up to temperature.

-Next remove all the spark plugs.

-I've read I need to open the carb(s) while cranking the engine, do I need to open all 3 carbs on the Six Pack?

I plan to remove the fuel line before the mechanical fuel pump (and run the engine until the fuel is out the carbs) to keep from pumping fuel into the wide open carbs while cranking the engine?

I've read if I have a low reading add a little oil into the cylinder and retest?
If I then get a higher reading that would indicate a piston ring issue?

Anything I'm missing?

The engine is a stock bore 1966 440 with it's original 516 heads, what readings should I be looking for?

Thanks.

[KillerBee]

repost

[Chryco Psycho]

It helps to have 1 carb open so the engine can easily pull in air , you will not flood the engine with the fuel line on very little fuel will be drawn into the air flow @ cranking speed .
 I would expect to see around 150 PSI depending what cam is in the engine , a variation of up to 15% is considered acceptable although less is better . Adding oil to the cjhamber will help seal the rings & can boost the readings If the rings are bad , if you have valve issues the reads will not change typically . Do you suspect the engine has a problem or just checking it ?

[KillerBee]

It helps to have 1 carb open so the engine can easily pull in air , you will not flood the engine with the fuel line on very little fuel will be drawn into the air flow @ cranking speed .
 I would expect to see around 150 PSI depending what cam is in the engine , a variation of up to 15% is considered acceptable although less is better . Adding oil to the cjhamber will help seal the rings & can boost the readings If the rings are bad , if you have valve issues the reads will not change typically . Do you suspect the engine has a problem or just checking it ?

I'm starting to notice some smoke out the tail pipes and smells a little rich.

Engine bottom end is a completely untouched stock(including bore) 1966 440 (with 516 heads)
Engine has about 80k original miles on it, got it out of a low mile 1966 New Yorker.

Cam is a MP .528 solid
Heads had the larger exhaust valves installed and freshend about 10 years ago.

Vacuum has always been  low at 7-8 measured off the intake port below rear carb.

Have never been able to get the carbs adjusted 100%
Adjusting air screws on center carb don't seem to change anything, got them set at 1 1/2 turns out.
I've tried your suggested weld wire in the air bleeds with no success.
Carbs were new and are clean inside and out.

Again car currently runs great, (besides the smoke out the tail pipes) idles rock steady at around 1000 rpm and actually runs cooler that I want at 160 degrees, even in hot weather.

I figured a compression check wouldn't hurt if that turns out good I might pull the heads over the winter and have them checked and gone through again??

[Chryco Psycho]

Smoke could be oil or fuel , I have done some great porting on the 516s to get very good airflow through them
try a 4.5 power valve in the center carb , easiest to remove the rear carb to get to the center one 

[72cudamaan]

If the exhaust smells rich then the smoke might be related to the smell and oil consumption. Do your plugs look oil fouled?
or it might be valve seals and you don't have to pull the heads. 

[KillerBee]

Smoke could be oil or fuel , I have done some great porting on the 516s to get very good airflow through them
try a 4.5 power valve in the center carb , easiest to remove the rear carb to get to the center one

Currently has a 4.5 power valve.

Plugs do look a little darker than I would like.

Distributor has vacuum advance unhooked, light springs installed and timing set at 38 at idle.




It's hard to believe how quickly the years go by.

This engine has a strong running history and I've been running it in a few different vehicles for 11 years now .

I had it in another street/strip Challenger of mine with a MP .509 cam, single plane intake and Holley 750DP
Hemi 4 speed, SS springs, heavy all steel street car.

Car ran 11.80 (with daylight under the front tire) first time out, driven to the track no tuning.
I think I could have gotten 11.50's out of it with some tuning and better air but never got the chance to take it back to the track.
Not bad for a stock bore 440 in a heavy street car.

With the current Six Pack , .528 cam and 3.91 rear gear it runs very good but the car doesn't feel near as strong as before.

Maybe the old engine is finally getting tired.
Would be nice if it just needs valves seals or the heads gone through.
How can I check the valve seals?

We'll see what the compression looks like.



Thanks.

[Strawdawg]

Timing is 38 degs at idle?

[KillerBee]

Timing is 38 degs at idle?

Yes

[bandt]

That is a lot of initial timing.
 
Doesn't seem right, that would be ok for total timing.

[Strawdawg]

that is a lot for total timing as well...even if the mechanical advance is locked...total timing normally works out around 34-36 on a 440 from what I have seen

Sure hope your mechanical advance is welded up, or locked out in some manner

16 degs of inital advance and 18-20 more from the distributor usually works pretty well for a street car

[KillerBee]

I've had that timing setup for 10 years now with no problems.

Car has always run strong with great street manners.

Setup was suggested  by one of the best in the buisness.

We took factory distributor apart, made sure everything was in good working order and not worn,  installed lighter springs(I think they were from Moroso).

Plugged the vacuum advance port.

Used a digital timing light set to 37 or 38 advance and set the mark on the balancer at 0, seems to like 38 the best.

No pinging or issues, always ran great.

[Strawdawg]

That is total timing then .  You posted you had 38 degs at idle

[KillerBee]

That is total timing then .  You posted you had 38 degs at idle

Well I set the timing to 38 degrees at idle, right around 1000 rpm.

The springs in the distributor are so light timing is all in at idle.